Synthesis, Characterization and Study of Cadmium and Zinc Sulphide Multilayer Thin Film using CBD

Abstract

I.INTRODUCTION Broad information over the thin film of nanomaterials is a significant aspect in crafting devices with required functions. Due to this motive, well-organized efforts have been made to produce thin films in nanoscale. The assembly of thin films one over the other also called as multilayer thin films have some enhanced properties than a single layer thin film. In recent time's cadmium and zinc chalcogenides have found a vast area for research [1]. The reason behind the wide research is possiblities for their applications in the field of optical and electronic devices. CdS is a good candidate for wide band gap material for photovoltaic and photoconducting devices. Its band gap ranges from 2.37 to 2.43 eV. The addition of ZnS to CdS enhances the band gap and hence can reduce the absorption losses. Zinc sulphide itself has a band gap of 3.65 eV. Various deposition techniques such as spray pyrolysis, metal organic chemical vapour deposition (MOCVD) and chemical bath deposition (CBD) have been used to deposit Cadmium Sulphide and Cadmium Zinc Sulphide thin films [2]. The chemical bath deposition (CBD) technique due to its moderately low cost and simple method for the deposition of high quality and large area films is used as the synthesis technique. In present work, thiourea is used as the sulphiding agent. The assembly of thin films, in other words the multilayer thin film is deposited on glass substrate. The layers are a combination of different ratio of cadmium sulphide and zinc sulphide. The wide bandgap CdZnS thin films have been widely used as a buffer and window material in hetero-junction solar cells and in photoconductive devices [3]. In this present work we describe the deposition of CdS and Cd-ZnS thin films by CBD method and compare their structural and optical properties with parameters like thickness crystallite size, lattice constant, band gap energy etc.